Aquatic ecosystems are becoming increasingly polluted with heavy metals from stormwater runoff and wasterwater input. The transfer of heavy metals through food webs has detrimental effects on organism diversity. This project conducted both a field study and laboratory experiments to explore the biouptake of copper (Cu) and zinc (Zn) in urban stream food webs. A field survey was conducted in summer 2014 to study the biodiversity of benthic macroinvertebrates in upstream and downstream sites of nine impaired streams. Two laboratory experiments were also conducted in Fall 2015. One studied the biouptake of heavy metals using periphyton collected from the Park River in culture with wastewater from a wastewater treatment plant. Water quality (turbidity, nitrates, total phosphate) and Cu and Zn concentrations in water and periphyton were measured to compare groups with wastewater and water from the Park River. The other experiment used the cultured periphyton to feed benthic macroinvertebrates to simulate the trophic transfer of heavy metals through urban stream food webs.
Results/Conclusions
The results from the field survey showed higher species richness when comparing upstream and downstream of all nine streams. Among the nine streams, six showed a lower species richness, Shannon-Weaver Diversity Index, and evenness in the downstream indicating impairment of those streams. Experiment results showed significantly higher turbidity and nitrate concentrations in undiluted wastewater compared to diluted wastewater and stream water; no significant correlation was found regarding total phosphate. Undiluted wastewater was found to have significantly higher concentrations of Cu and Zn compared to diluted wastewater and stream water. Additionally, the periphyton biouptake of heavy metals showed a higher concentration of Cu uptake in undiluted wastewater compared to diluted wastewater and stream water. However, no significant difference was found in Zn uptake. Contrary to prediction, benthic macroinvertebrates contained higher concentrations of Cu and Zn in stream water compared to undiluted wastewater. Overall, these findings demonstrated transfer of heavy metals from water to periphyton and to benthic macroinvertebrates in urban stream food webs and stormwater and wastewater runoff had negative effects on diversity of macroinvertebrates.